1. Field
The present disclosure relates to stretchable channel composites capable of being used as channel materials for transistors and methods of preparing the stretchable channel composites. The provided channel composites are stretchable and may be used for stretchable transistors. Also, the provided channel composites may be applied in robotic sensory skins, electronic textiles, and implantable medical devices.
2. Description of the Related Art
Most electronic devices are based on a silicon substrate. Methods of silicon growth are well established and a silicon substrate may be manufactured by a simple manufacturing process. A thin film transistor (TFT) is an active element and is a necessary component in a display device. As such, a TFT will be a necessary component in various next-generation applied fields requiring transparency, flexibility, and stretchability. Accordingly, TFTs represent a very important field of technology requiring continuous research and development. In a TFT, an improved silicon substrate, such as an amorphous silicon substrate, a low temperature poly silicon substrate (LTPS), or the like may be used. Unfortunately, however, typical inorganic materials generally fracture or transform under a strain of about 1%. Likewise, a silicon substrate, such as an amorphous silicon substrate or a LTPS, fracture or transform under a strain of about 1%. Accordingly, a silicon (Si)-type traditional material is not used in stretchable electronics.
In a the future, various forms of display devices (for example, a transparent displaying device or a flexible display device that can be attached to a wide wall, a curved pillar, or a ceiling) will play a very important role. By using a bendable plastic substrate and an easily-produced organic thin film, various forms of flexible devices may be manufactured at low cost. Plastic substrates and organic thin films are foundations of organic electronics. Also, in order to obtain a stretchable TFT, an approach through organic electronics is needed.
Stretchable electronics may be divided into a number of categories. The most technically useful electronics are applied products that are strong against stress and are slightly bendable. The next challenge is to produce bendable and rollable devices; the most difficult challenge is to produce foldable and stretchable devices into a desired form. Here, a technical issue to be considered is the mechanical strain applied to the substrate or to a deposited thin film. The strain that arises when a substrate having a thickness of L is bent with a radius of curvature R is defined as L/2R. When the substrate is folded, the strain applied to the substrate may increase greater than by ten times compared to when the substrate is simply bent. When the substrate is stretched or transformed into a desired form, the strain may increase up to 100%. Depending on the degree of applied strain, different measures need to be taken, and the thus the goal of the stretchable electronics field is to use suitable organic materials.
Other advantages that arise when organic materials are used include that various printing methods become available, as well as low processing temperature and solution processing. Hence, when equipment having numerous vacuum devices is replaced with a simple solution process or a printing process, it is possible to substantially reduce manufacturing costs.
However, pre-existing organic semiconductor materials that may be used for a channel layer of a TFT are either not stretchable or are very weak. P3HT(poly(3-hexyl thiophene)) is representative of such organic semiconductor materials. Regarding P3HT, when elongation is 3%, conductivity is reduced substantially as the number of stretches increases, and when elongation reaches 5%, the conductivity disappears after only one stretch.